It is known to have power elevators on hospital stretchers, beds, drafting tables, barber chairs, etc. Examples of such power elevators are U.S. Pat. Nos. 2,592,166; 3,707,930; and 3,888,444. Because of the particular use, many of these elevators are required to have very compact dimensions and often support a cantilevered table similar to the cantilevered structure of an automobile lift used in gasoline stations. Such "central post" elevators provide convenient access about an entire periphery of the table without bumping into corner supports, such as in the four poster bed of U.S. Pat. No. 2,592,166. This is very important in hospital stretchers where nurses and physicians must have easy 360.degree. access around a patient. Also, the cantilevered areas provide easy access to suspended urinary drainage containers and permit other medical carts and equipment to be rolled very close to the stretcher from all directions.
A single center post elevator has practical advantages over 4 widely spaced elevators at corner posts, such as in U.S. Pat. No. 2,592,166. The narrow spindle-like legs of this patent would tend to wobble, and also any torque in the elongated shaft extending the length of the bed and any play in the worm gears could cause uneven vertical motion among the 4 spindle-like legs resulting in binding.